Gear Pump

ABSTRACT

A gear pump is described with a plurality of gear wheels which intermesh in order to deliver a pumping medium, and are rotatably held in a pump case and deliver a pumping medium from a priming zone into a delivery pressure zone of the pump case. One of the gear wheels is driven by a pump shaft which protrudes with a coupling end out of the pump case. In order to seal the pump case, a shaft sealing ring is held around the circumference of the pump shaft, wherein according to the invention, in order to avoid material deposits, the shaft sealing ring is associated with an interior flushing chamber on the circumference of the pump shaft, the flushing chamber being connected to the delivery pressure zone of the pump case by a feed channel in the pump case.

This application is a continuation-in-part of and claims the benefit of priority from PCT application PCT/EP2011/060133 filed Jun. 17, 2011 and German Patent Application DE 10 2010 025 865.2 filed Jul. 2, 2010, the disclosure of each is hereby incorporated by reference in its entirety.

BACKGROUND

The invention relates to a gear pump.

It is known to use gear pumps to deliver and dispense fluids with several gear wheels which intermesh, said gear wheels delivering the fluid between a priming zone and a delivery pressure zone. To this end at least one of the gear wheels is driven by a pump shaft which is connected to a drive arranged outside of the pump housing. Such pump shafts are mounted in the pump housing and sealed vis-à-vis the environment by shaft sealing rings. The shaft sealing ring prevents the escape of the delivered fluid during operation, said fluid reaching through leakage flows through the bearing positions of the pump shaft and settling directly in the region before the shaft sealing ring.

In order to make possible a regular exchange of such leakage flows, a gear pump is known, for example, from EP 0 669 465 A, in which the leakage flow flowing through the bearing position of the pump shaft is conducted into an annular space which is connected to the suction side of the pump via a return channel. However, such return systems basically have the disadvantage that a higher differential pressure predominates on the bearing position of the pump shaft, so that this is accompanied by an increase of the leakage flow. In addition the possibility cannot be ruled out that material deposits will form on the shaft sealing ring which are not exchanged there and depending on the pumping medium lead to solidifications which prematurely seal the sealing lip of the shaft sealing ring.

From WO 2007/131994 A1 a further gear pump is known, in which the return system is supported by a return conveyor threading on the circumference of the pump shaft. In this connection the leakage flow flowing through the bearing position of the pump shaft is directly conducted into a return section which is constructed on the pump shaft between the shaft sealing ring and the bearing position. The return section is connected to a suction side of the pump via a return channel. In this respect in the return conveyor section an opposing return flow is generated which returns the pumping medium penetrating through the bearing position. However, such systems require the construction of return conveyor threading in the circumference of the pump shaft which entails a high production expenditure.

Hence the problem addressed by the invention is that of improving a gear pump of the generic type in such a way that possible material deposits of the pumping medium in the region of the shaft sealing ring during operation are prevented.

SUMMARY

In accordance with the invention this problem is solved by arranging an interior flushing chamber on the circumference of the pump shaft which is connected to the delivery pressure zone in the pump housing by a feed channel.

Advantageous improvements of the invention are defined by the features and feature combinations as described in the specification.

The invention has the special advantage that a continuous flushing flow can be fed to the shaft sealing ring, said flushing flow being formed from the pumping medium. Hence the fluid can be prevented from staying in dead spaces before the shaft sealing ring. The inventive gear pump is therefore especially beneficial for delivering fluids which, in the event of staying in pump dead spaces, have a tendency to form solids or harden, as for example is the case with adhesives.

The advantageous improvement of the invention, in which the flushing chamber is connected to the priming zone in the pump housing by a return channel, guarantees a continuous exchange of the flushing flow within the flushing chamber, so that the shaft sealing ring is continuously flushed on its interior. The pressure differential generated via the feed channel and the return channel guarantees an uninterrupted continuous flushing flow from the delivery pressure zone to the suction zone of the pump.

To achieve the smallest possible volume flows the improvement of the invention is preferably used, in which the feed channel and/or return channel each flow into a region of a stop face of a housing plate, which cooperates on the front side with the gear wheel held on the pump shaft. Thus leakage flows appearing in the delivery pressure zone between the gear wheel and the case plate can be tapped in order to generate flushing flow. In addition, the stop gap between the gear wheel and the case plate guarantees a decrease in pressure so that flushing flows with lower pressure levels can also be achieved in the case of higher operating pressures.

In order to be able to uniformly flush the entire annular space of the flushing chamber before the shaft sealing ring, the feed channel and the return channel flow at an angular offset of 180° into the flushing chamber.

The differential pressures predominating for the formation of a flushing flow can also be influenced in an advantageous manner as a result of the fact that the feed channel and/or the return channel each are formed with a throttle. In this way, small volume flows can be advantageously produced which, in particular, are suitable for the flushing of small flushing chambers. With this, the losses caused in the event of the delivery by the flushing flow can be reduced to a minimum.

Particularly advantageous is the improvement of the invention in which the throttle is formed by a throttle bore in a filler ring, said filler ring being associated with the flushing chamber of the mouth of the feed channel and/or of the mouth of the return channel. With this, very small free spaces to the shaft sealing ring can be realized within the flushing chamber which can only be flushed out by correspondingly small flushing flows.

The filler ring in the process advantageously has two throttle bores facing one another which are directly associated with the feed channel and the return channel. The use of a filler ring has the special advantage that an individual design and size of the free space formed in the flushing chamber for flushing of the interior of the shaft sealing ring can be created.

Thus, the improvement of the invention has proven to be especially easy to install, in the event of which the shaft sealing ring is held by a seal housing which is firmly connected to the pump housing and penetrated by the pump shaft.

In order to realize a concentric arrangement of the shaft sealing ring to the pump shaft vis-à-vis the bearing bores, the seal housing has a centering collar which forms the flushing chamber. The centering collar is held in a centering section of the pump housing and is used advantageously for fixation of the filler ring so that said filler ring can be held in the base of the centering section directly before the mouths of the feed channel and of the return channel.

In the case of the inventive gear pump conventional shaft, sealing rings can be used for sealing of the pump housing. However, the possibility also exists that the shaft sealing ring is formed by seal packs or several seal systems. Thus in the case of an advantageous improvement of the invention a second shaft sealing ring can be arranged within the seal housing, wherein between the two shaft sealing rings on the circumference of the pump shaft a separation chamber is constructed which is filled with a separation medium. Thus the inner shaft sealing ring can be completely shielded from the environment, so that pumped media which is highly reactive can be securely delivered.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive gear pump will be described more closely in the following with the help of some exemplary embodiments with reference to the attached figures.

The figures show the following:

FIG. 1 shows schematically a cross-sectional view of a first exemplary embodiment of the inventive gear pump.

FIG. 2 shows schematically a sectional view of the gear pump of the exemplary embodiment according to FIG. 1.

FIG. 3 shows schematically a sectional view of a further exemplary embodiment of the inventive gear pump.

FIG. 4 shows schematically a section of a further exemplary embodiment of the inventive gear pump.

DETAILED DESCRIPTION

FIG. 1 and 2 show a first exemplary embodiment of the inventive gear pump. FIG. 1 shows schematically a cross-sectional view of the gear pump and in FIG. 2 a sectional representation of the gear pump is shown on a sectional plane 90° offset to the cross-sectional view.

The gear pump consists of a pump housing 1. The pump housing 1 is built in multiple parts and has several housing plates 1.1, 1.2 and 1.3, which are connected to one another by several bolts 23. Within a center housing plate 1.3 a recess for two intermeshing gear wheels 3 and 4 is contained. The center housing plate 1.3 is held with the gear wheels 3 and 4 between the outer housing plates 1.1 and 1.2. One of the gear wheels 3 is rotatably arranged on a bearing journal 6. The bearing journal is, to this end, held in a journal bore 7.1 of the outer housing plate 1.2 and in a journal bore constructed as a blind hole in the opposing outer housing plate 1.1. The second gear wheel 4 is arranged rotationally fixed on a pump shaft 5. The pump shaft 5 is provided with a plurality of shaft sections rotatably mounted in the housing plates 1.1 and 1.2 To this end, the housing plate 1.1 has a first bearing bore 8.1 and the second housing plate 1.2 has a second bearing bore 8.2, each of which completely penetrate the housing plates 1.1 and 1.2. The pump shaft 5 penetrates the housing plate 1.1 and protrudes outside of the pump housing with a coupling end 5.1. The coupling end 5.1 can be coupled to a drive not shown here.

On the opposing side of the pump housing 1, a pump inlet 2 and a pump outlet not shown here are constructed on the pump housing 1. The pump inlet 2 as well as the pump outlet that is not shown here penetrate the outer housing plate 1.2 and flow within the pump housing 1 into a suction zone and an opposing delivery pressure zone. A connection surface 9 is constructed on the outer housing plate 1.2 for connection of the pump, into which both the pump inlet 2 and the pump outlet flow.

A shaft sealing ring 12 is arranged on the circumference of the pump shaft 5 for sealing the pump housing 1 from the coupling end 5.1. To this end, the shaft sealing ring 12 is held between the housing plate 1.1 and the pump shaft 5.

On the interior of the shaft sealing ring 12 concentric with the bearing bore 8.1, a circulating flushing chamber 11 to the pump shaft 5 is formed in the housing plate 1.1.

As can be seen from the representation in FIG. 2, the flushing chamber has a feed channel 13 associated with it. The feed channel 13 flows with one end into the flushing chamber 11 and with the opposing end into a stop face 15 for the gear wheel 4 of the housing plate 1.1. The feed channel 13 flows into a region of the stop face 15, which is connected to the delivery pressure zone of the pump housing 1. In this respect the feed channel 13 constitutes a connection between the delivery pressure zone and the flushing chamber 11.

On the opposing side of the pump shaft 5 a return channel 14 is provided at an angular offset of 180° in the housing plate 1.1, said return channel flowing with one end into the flushing chamber 11 and with the opposing end flowing into the stop face 15 of the gear wheel. The return channel 14 flows into a region of the stop face 15 in which said face is connected to the suction zone via the gap. Hence a pressure differential can be generated within the flushing chamber 11 which makes the supply and removal of a flushing flow possible.

In the exemplary embodiment shown in FIGS. 1 and 2 the axial forces applied on the pump shaft 5 are absorbed by a snap ring 10 which is arranged between the pump shaft 5 and the housing plate 1.2.

In operation, a pumping medium flows via the pump inlet 2 and pumped within the pump housing 1 through the gear wheels 3 and 4 from a suction zone to a delivery pressure zone. The pumping medium is dispensed through the pump outlet via the delivery pressure zone. In this situation leakage flows occur in the gaps between the pump housing 1 and the gear wheels 3 and 4, the leakage flows which regularly travel from a high-pressure side to a low-pressure side in the pump housing 1 due to the existing pressure differential between the delivery pressure zone and the suction zone. Thus, the bearing positions of the pump shaft 5 in bearing bores 8.1 and 8.2 are lubricated by leakage flows of the pumping medium. On the housing plate 1.2 the sealing takes place via a flange which is adjacent to the connection surface 9. On the opposing housing side, the sealing of the pump housing 1 takes place through the shaft sealing ring 12. In order to prevent possible material deposits on the interior of the shaft sealing ring 12 by the leakage flow of the pumping medium through the bearing bore 8.1, a continuous flushing flow is generated from the pumping medium in the flushing chamber 11. The flushing flow generated from the leakage in the gaps is conducted via the feed channel 13 to the flushing chamber 11 and is returned via the return channel 14 to the low-pressure side of the pump housing 1. Thus, longer residence times and with this corrosion or aging of the pumping medium in the region of the shaft sealing ring 12 can be prevented. The shaft sealing ring 12 is continuously flushed with fresh pumping medium.

The inventive gear pump is therefore especially well suited for the pumping of pumping media in which case already short residence times to chemical reactions which in particular lead to material hardening. It is known that hardened material deposits in the region of the shaft sealing rings lead to increased wear and tear. This is advantageously prevented by the continuous flushing of the shaft sealing ring on the interior.

In FIG. 3, a further exemplary embodiment of the inventive gear pump is shown schematically in a sectional view. The exemplary embodiment is essentially identical to the exemplary embodiment for FIGS. 1 and 2 so that only the differences will be mentioned here.

In the case of the exemplary embodiment shown in FIG. 3 a seal housing 18 is provided for accommodation of the shaft sealing ring 12. The seal housing 18 is firmly connected to the pump housing 1. In this regard, the exterior housing plate 1.1 has a centering section 19 in which a centering collar 20 of the seal housing 18 meshes. The seal housing 18 has a stepped bore 24 for accommodation of the shaft sealing ring 12, with the stepped bore penetrating the centering collar 20.

A filler ring 16 is arranged between the housing plate 1.1 and the seal housing 18, with the filler ring being held via a brace 16.1 between the centering section 19 and the centering collar 20. The filler ring 16 has two throttle bores 17.1 and 17.2 constructed offset to one another by 180°, said throttle bores flowing on the sides facing the centering section 19 to the feed channel 13 and the return channel 14. On the opposing front side of the filler ring 16 a flushing chamber 11 is formed between the shaft sealing ring 12 and the filler ring 16 within the seal housing 18. The throttle bores 17.1 and 17.2 flow into the flushing chamber 11 so that a flushing flow flows throttled via the feed channel 13 into the flushing chamber 11. The flushing chamber 11 is in this exemplary embodiment constructed with a minimum amount of free space so that even the smallest volume flows of the flushing flow are sufficient to flush the region of the interior of the shaft sealing ring 12.

In the case of the return of the flushing flow via the return channel 14 the second throttle bore 17.2 is provided in order to obtain an intensive distribution of the flushing flow within the flushing chamber so that the entire circumferential region of the sealing shaft ring 12 is flushed. The throttle bores 17.1 and 17.2 in the filler ring 16 are constructed on the filler ring 16 offset to one another by 180°. Depending on the requirements, the throttle bores 17.1 and 17.2 can have equally large opening cross-sections or different opening cross-sections.

Hence, the exemplary embodiment of the inventive gear pump shown in FIG. 3 has the special advantage that small volume flushing flows and with that minimal leakage are generated in order to make possible an intensive flushing of the shaft sealing ring 12. Due to the throttles associated with the feed channel 13 small volume flows can also be achieved in the event of high operating pressures.

FIG. 4 shows another exemplary embodiment of the inventive pump in a partial sectional view of the pump shaft. The exemplary embodiment is essentially identical to the exemplary embodiment according to FIG. 3, so that reference is made to the aforementioned description and only the differences will be explained here. In comparison to the exemplary embodiment according to FIG. 3, the sealing of the pump housing 1 from the environment on the pump shaft 5 is expanded in such a way that in the seal housing 18 a second shaft sealing ring 22 is held. The shaft sealing rings 12 and 22 are held at a distance from one another on the circumference of the pump shaft 5 by the seal housing 18. Between the two shaft sealing rings 12 and 22 a separation chamber 21 is constructed on the circumference of the pump shaft 5 by the seal housing 18. A separation fluid 25 is held within the separation chamber 21, with the separation fluid resulting in the shielding of the inner shaft sealing ring 12 from the environment. In this respect, improved sealing is achieved which is particularly advantageous in the case of highly reactive pumping media.

It is expressly pointed out here that the exemplary embodiments of the inventive gear pump according to FIGS. 1 through 4 shown are exemplary in their constructive design. A prefabricated construction of the housing, for example, is not absolutely necessary. However, it is essential that an interior of the shaft sealing ring in the pump shaft is continuously flushed via a flushing flow which is fed directly from the pumping medium. In this respect, the arrangement and construction of the feed channel and of the return channel can be designed in such a way that they flow directly into a pressure chamber of the delivery pressure zone or a suction space of the suction zone. Thus a plurality of feed channels or also a plurality of return channels can be also be advantageously integrated in a pump housing.

REFERENCE LIST

-   1 Pump housing -   1.1 Exterior housing plate -   1.2 Exterior housing plate -   1.3 Center housing plate -   2 Pump inlet -   3 Gear wheel (rotating) -   4 Gear wheel (driven) -   5 Pump shaft -   5.1 Coupling end -   6 Bearing journal -   7.1, 7.2 Journal bore -   8.1, 8.2 Bearing bore -   9 Connection surface -   10 Snap ring -   11 Flushing chamber -   12 Shaft sealing ring -   13 Feed channel -   14 Return channel -   15 Stop face -   16 Filler -   16.1 Brace -   17.1 17.2 Throttle bore -   18 Seal housing -   19 Centering section -   20 Centering collar -   21 Separation chamber -   22 Second shaft sealing ring -   23 Bolts -   24 Stepped bore -   25 Separation fluid 

1. A gear pump comprising: a plurality of intermeshed gear wheels that are rotatably held in a pump housing to deliver a pumping medium from a priming zone into a delivery pressure zone of the pump housing; a pump shaft for driving one of the gear wheels, wherein the pump shaft has a coupling end protruding from the pump housing and a shaft sealing ring held on the circumference of the pump shaft for sealing the pump housing; and an interior flushing chamber about the circumference of the pump shaft and associated with the shaft sealing ring, the flushing chamber being connected to the delivery pressure zone of the pump housing by a feed channel in the pump housing
 2. The gear pump according to Claim 1, wherein the flushing chamber is in fluid communication with the priming zone of the pump housing by a return channel in the pump housing.
 3. The gear pump according to Claim 1, wherein at least one of the feed channel and the return channel flow into a region of a stop face of a housing plate of the pump housing which cooperates on the front side with the gear wheel held on the pump shaft.
 4. The gear pump according to Claim 1, wherein the feed channel and the return channel flow into the flushing chamber at an angular offset of 180°.
 5. The gear pump according to Claim 1, wherein at least one of the feed channel and the return channel have a throttle.
 6. The gear pump according to claim 5, wherein the throttle is formed by a throttle bore in a filler ring, the filler ring being associated with the flushing chamber of one of a mouth of the feed channel and a mouth of the return channel.
 7. The gear pump according to claim 5, wherein the filler ring has two throttle bores facing one another wherein one is in fluid communication with the feed channel and the other is in fluid communication with the return channel.
 8. The gear pump according to Claim 1, wherein the shaft sealing ring is held by a seal housing that is connected to the pump housing and penetrated by the pump shaft.
 9. The gear pump according to claim 8, wherein the seal housing has a centering collar forming the flushing chamber, said centering collar meshing in a centering section of the pump housing and fixedly holding the filler ring via a rotating brace.
 10. The gear pump according to claim 8, wherein a second shaft sealing ring is held within the seal housing and a separation chamber is constructed between the two shaft sealing rings on the circumference of the pump shaft. 